Harness, oh YES!

For water, I use one of these:

http://www.drsfostersmith.com/produc...cfm?pcatid=900

You can get them plenty of places, not just Foster & Smith. The 17 ounce should be fine, I use the larger one as I have 5 dogs, lol.

Just checked, it is on sale on Amazon.com
http://www.amazon.com/Handi-Drink-Do.../dp/B000GDXHQ0

On the bike trail, you will need poop bags too!
http://www.amazon.com/Bags-Board-Bon...ref=pd_sim_k_3

Again, lots of places to buy them.

And you will need treats with you. Mikey is in training; some claim (and I am one of them) dogs are in training all their lives, lol. Don't know if you will rely on baggies in your pockets, or if you want a clip on treat bag something like this
http://www.amazon.com/Guardian-Gear-.../dp/B001TH6Q1K

That one clips around your waist; other styles clip to your belt.

For Mikey, you may want a long line. Easy to make your self.
1. Clip together a few leashes! or
2. Get a length of rope, maybe 20 feet long. Buy one of these clips for the end:
http://www.seattlefabrics.com/leash%20clips.html
Be sure to get one that swivels. The other end, knot it with a loop, and attach his leash to it, so you have a nice hand grip.

The idea is, he has some leeway to explore and "be a dog." Plus he is a beagle mix so he wants to investigate everything his nose scents. You don't have to get "up close and personal" with all the "P-mail" he has to check out, ha haaa.

Then, just have some fun!